C2.1-Atoms and Reactions Flashcards
C2.1.1-What is an Isotope?
An isotope is an atom of an element with the same amount of protons but a different amount of neutrons.
C2.1.1-What is the atomic structure and their charges?
The atom consists of a nucleus made up of protons and neutrons with electrons around the nucleus in shells.
Proton: +1 charge, 1 mass, Neutron: 0 charge, 1 mass, Electron: -1 charge, 1/1836th mass of proton
C2.1.1-What are chemical and physical differences in isotopes?
Different isotopes of the same element have the same number of electrons and therefore react in the same way as neutrons don’t have an effect on the reaction. There may be different physical properties as higher mass isotopes will have a higher melting point, boiling point and density.
C2.1.1-What is relative isotopic mass?
Relative isotopic mass is the mass of an isotope relative to 1/12th the mass of a carbon-12 atom.
C2.1.1-What is Relative atomic mass?
Relative atomic mass is the weighted mean mass of an atom of an element relative to 1/12th the mass of a carbon-12 atom.
C2.1.1-How does a mass spectrometer work?
A sample is placed in the mass spectrometer and it is vaporised and then ionised to from positive ions.
The ions are accelerated, heavier ions move more slowly and are more difficult to deflect than lighter ones so ions of each isotope are separated.
The ions are detected on a mass spectrum as a mass to charge ratio.
C2.1.2-What are some of the polyatomic ions?
Polyatomic: NO3-, CO3(2-), SO4(2-), OH-, NH4+,
Others: Zn2+, Ag+
C2.1.2-What are diatomic molecules?
Two atoms bonded together.
H2, N2, O2, F2, Cl2, Br2, I2.
C2.1.3-What is amount of substance?
Quantity used to count the number of particles in a substance measured in a unit called mole.
C2.1.3-What is a mole and the Avogadros constant?
One mole is the amount of substance that contains 6.02x10^23 particles. The Avogadros constant is 6.02x10^23 mol^-1 which is the number of particles in each carbon-12 mole.
C2.1.3-What is molar mass and molar gas volume?
Molar mass(g/mol^-1) is the mass per mole of a substance. Molar gas volume(Vm) is the volume per mole of gas molecules at a stated temp and pressure.
C2.1.3-What is hydrous?
A substance that contains water, either in its structure or as water of crystallisation.
Eg: Hydrated Copper(II) Sulfate(CuSO4 - 5H2O is blue because it has water of crystallisation
C2.1.3-What is anhydrous?
A substance that doesn’t contain water or water of crystallisation.
Eg: Anhydrous Copper(II) Sulfate(CuSO4) is white because it lacks water molecules.
C2.1.3-What is Water of Crystallisation?
Water molecules that are chemically bonded within the crystalline structure of a compound.
Eg: CuSO4 - 5H2O, the 5H2O molecules are water of crystallisation.
C2.1.3-How can a salt go from hydrous to anhydrous?
When blue crystals of hydrated copper(II) sulfate are heated, bonds holding the water within the crystal are broken off which drives the water off.
C2.1.3-How to carry out experiment that determines water of crystallisation in hydrated crystals?
Weigh an empty crucible. Add the hydrated salt into the weighed crucible and weigh the crucible and hydrated salt. Use a pipe clay triangle to support the crucible containing hydrated salt on the tripod. Heat crucible and contents gently for 1 min, then heat strongly for 3 mins. Leave crucible to cool and then weigh the crucible and anhydrous salt.
C2.1.3-What calculations are needed for Water of Crystallisation experiment?
Use mass values to find the mass of anhydrous salt and then find the moles with moles = mass(g)/mr. Then use mass values to find mass of water and find moles of water. Find smallest whole umber ratio and write formula down. (CuSO4 - 5H2O)
C2.1.3-What assumptions are made about the Water of Crystallisation experiment?
If hydrated and anhydrous salt have different colours, you can be sure when all water is removed. However if a similar colour, heat the crystals until mass of residue no longer changes suggesting water is removed. Many salts decompose further when heated such as copper(II) Sulfate decomposing to form black copper(II) oxide.
C2.1.3-List measurement conversions
cm^3 to m^3 — X 10^-6
dm^3 to m^3 — X 10^-3
C to K — +273
kPa to Pa — X 10^3
C2.1.3-How to find relative molecular mass
Add a sample of the volatile liquid to a small syringe via needle and weigh small syringe. Inject sample into a gas syringe through self sealing rubber cap. Reweigh the small syringe to find the mass of the volatile liquid added to the gas syringe. Place the gas syringe in a boiling water bath at 100 degrees. The liquid vaporises producing a gas and pressure is recorded. Then use pV=nRT to find moles and then mr.
C2.1.3-What are balanced equations used for?
They’re used to find the quantities of reactants required to prepare a required quantity of a product and the quantities of products that should be formed from certain quantities of reactants.
C2.1.3-How could you use an experiment to identify a metal?
Set up apparatus with gas syringe going into conical flash. Weigh sample of metal and add to flask. Use a measuring cylinder to add 25cm^3 of HCL to flask and quickly replace bung. Measure max volume of gas in syringe. Assume RTP and find moles, then make equation with HCL, X, Cl2 and H2.
C2.1.3-What is the limiting reagent?
It is the reactant not in excess which will be used up first and stop the reaction. You can find it out by calculating moles and comparing with equation.
C2.1.3-What are the benefits of a high atom economy reaction?
It produces a large proportion of desired products and few unwanted waste products. It it’s important for sustainability as they make the best use of natural resources. They make processes more efficient and preserve raw materials.
C2.1.4-What are strong and weak acids?
A strong acid releases all of its hydrogen atoms into solution as H+ ions and completely dissociates in aqueous solution. A weak acid only releases a small amount of its hydrogen atoms into solution as H+ ions and only partially dissociates in aqueous solution.
C2.1.4-What are the neutralisation reaction equations?
Acid + Base/alkali-> Salt + Water
Acid + Metal Hydroxide -> Salt + Water
Acid + Metal Oxide -> Salt + Water
Acid + Metal Carbonate -> Salt + Water + Hydrogen
C2.1.4-How do you prepare a standard solution for a titration?
The solid is weighed accurately and then dissolved in a beaker using less distilled water than needed to fill volumetric flask to the mark. This solution is transferred to a volumetric flask and last traces are rinsed into flask with distilled water. The flask is carefully filled to the graduation line by adding distilled water a drop at a time until the bottom of the meniscus lines up with the mark. Too much water can dilute solution. Finally, the volumetric flask is inverted several times to mix solution.
C2.1.4-How do you carry out an acid-base titration procedure?
Add a measured volume of one solution to a conical flask using a pipette. Add the other solution to a burette and record the initial burette reading to the nearest 0.5cm^3. Add a few drops of indicator to the solution in the conical flask. Run the solution in the burette into the solution in the conical flask, swirling to ensure mixing. Eventually the indicator changes colour at the end point of the titration and the endpoint is used to indicate the volume of one solution that exactly reacts with the volume of the second solution. Record final burette reading and subtract initial from final to get titre(volume of solution added from burette). A quick trial titration is carried out to find approx titre. The titration is then repeated accurately, adding solution drop wise until endpoint is reached. Further titrations are carried out until results are concordant(within 0.1cm^3).
C2.1.4-What are uncertainty values?
10cm^3 pipette : +/- 0.04cm^3
25cm^3 pipette : +/- 0.06cm^3
50cm^3 pipette : +/- 0.1cm^3
100cm^3 volumetric flask : +/- 0.2cm^3
250cm^3 volumetric flask : +/- 0.3cm^3
C2.1.4-How can you use titration to identity an unknown carbonate?
Prepare a solution of unknown carbonate in a volumetric flask. Using a pipette, measure 25cm^3 of your prepared solution into a conical flask. Using a burette, titrate this solution using 0.1mol dm^-3 hydrochloric acid. Analyse results to identify carbonate(mean titre).
C2.1.5-What is an oxidation number?
The number of electrons involved in bonding to a different element. Each atom in a compound has an oxidation number and the sum of the oxidation numbers equate to total charge.
C2.1.5-What is oxidation and reduction?
Oxidation is the addition of oxygen and loss of electrons. It is also an increase in oxidation number. Reduction is the removal of oxygen and increase in electrons. It is also a decrease in oxidation number.
